Visible Light Triggered, Catalyst-Free Approach for the Click Synthesis of Imidazole-Fused Nitrogen-Bridgehead Nucleus in EtOH:H2O Medium

Abstract

Here, we have succeeded in developing an eco-efficient, mild, and metal-free synthetic protocol for biologically significant scaffolds: imidazopyridines and their derivatives via radical cyclization from a wide variety of simple 2-aminopyridines and phenacyl bromides as reactants and utilizing visible light as a reaction promoter in the ethanol/water solvent. To the best of our knowledge, the present strategy is the first example of visible light promoted synthesis of imidazo[1,2-a]pyridine via the formation of C-N bonds. The proposed methodology has various advantages namely quick reaction time, low cost, simple setup, high atom efficiency, easy-availability of reactants and non-involvement of specific glasswares and photo reactor system.